A sensor unit (50), a device, and a process for inspection of a surface (10′, 10&Dgr;) of an object (10) for the purpose of identifying surface characteristics, such as structural defects. The device contains an emitting module (51) and a receiving module (52). The emitting module emits at least one beam bundle (6, 6′, 6″). The receiving module has at least one light receiver (15, 16, 20). A rotating polygonal mirror wheel (2) is located in the focal point of a parabolic mirror (1). A beam bundle (6) of the laser (3, 4) is directed onto the mirror (1) by means of a telecentric lens, which guides the emitter and receiver beam on the same optical axis, whereby the parabolic mirror (1) guides the deflected beam bundle (6, 6′, 6″) under a constant angle relative to the axis of symmetry (7) of the parabolic mirror (1) along a scanning line (23, 24) over the object (10). The diffusely reflected beam bundle, after being deflected out of the common beam path, impinges on the processing unit (5).
Legal claims defining the scope of protection, as filed with the USPTO.
1. A device for inspecting a surface of an object to determine surface characteristics of the object, said device comprising: a scanning device, and an optical sensor unit comprising: a sending module for emitting light to the scanning device, a receiving module for receiving light incident from the scanning device, and an optical deflecting element that is operable to split light incident from the scanning device into a first beam path and a second beam path, said first beam path being different than said second beam path, said first beam path being defined by a first spatially limited part of the incident light and said second beam path being defined by a second spatially limited part of the incident light, and where the first spatially limited part has a cross sectional area that is smaller than a cross sectional area of the second spatially limited part, wherein the scanning device includes: a light deflecting element, said light deflecting element having a time-dependent deflection angle, and a concave mirror having a focal point and an axis of symmetry ( 7 ), wherein said light deflecting element is located in said focal point so that light emitted from the sensor unit can be guided into the sensor unit under a constant angle relative to the symmetry axis of the concave mirror along a scanning line over the object and so that light diffusely scattered from the object emanating from the scanning device can be guided into the sensor unit along a path identical to the emitted light and wherein the concave mirror is disposed relative to the object surface and the receiving module such that the surface can be telecentrically projected into the receiving module and the light deflecting element acts as an aperture diaphragm, said receiving module further comprising at least one light receiver with a special filter or a diaphragm designed and positioned in a manner that directly diffusely scattered light is blanked out for said at least one light receiver, in order to detect tracheid scattered light.
2. The device according to claim 1 , wherein the deflecting element is a mirror with an aperture and is positioned such that a major portion of light traveling from the emitting module to the deflecting element passes through the aperture to the scanning unit.
3. The device according to claim 1 , wherein the deflecting element is a mirror and is positioned such that a major portion of light traveling from the sending module to the deflecting element is reflected to the scanning device by the mirror.
4. The device according to claim 1 , wherein the emitting module includes a plurality of light sources that produce light having different wave lengths.
5. The device according to claim 4 , wherein said plurality of light sources includes at least a first light source and a second light source, said first light source emits light having a wave length between about 620 nm and 770 nm, and said second light source emits light having a wave length above 770 nm.
6. The device according to claim 1 , wherein the receiving module includes an optical system, the optical system being positioned between said deflecting element and said at least one light receiver such that the at least one light receiver is disposed in the focal plane of the optical system.
7. The device according to claim 6 , wherein the receiving module includes several light receivers and at least one beam splitter, whereby by means of said at least one beam splitter, light impinging on the receiving module can be split up among the light receivers.
8. The device according to claim 7 , wherein the at least one beam splitter has a wave length dependent reflection to transmission ratio.
9. The device according to claim 7 , wherein a further spatial filter or diaphragm is positioned ahead of a light receiver for blanking out light cones from a scatter effect.
10. The device according to claim 1 , including two light receivers, each of said two light receivers having a spatial filter or diaphragm arranged in a manner that directly diffusely scattered light is blanked out, said spatial filters being positioned orthogonally relative to one another to measure directional dependence of tracheid scattered light.
11. The device according to claim 1 , wherein the receiving module includes at least one CCD camera or at least one position-sensitive receiving element.
12. The device according to claim 1 , wherein the light deflecting element is a rotating polygonal mirror wheel.
13. The device according to claim 1 , wherein the concave mirror is a strip having parallel cut edges out of a paraboloid.
14. The device according to claim 1 , wherein, for obtaining a 3D profile by a triangulation process, at least one light beam emitted from the sensor unit can be guided on to the object and light diffusely scattered from the object under a constant angle ( ) relative to the incident beam can be guided back to the sensor unit such that the incident beam and the guided back beam are coincident in a plane parallel to the surface of the object.
15. The device according to claim 14 , wherein, for obtaining a telecentric 3D profile by means of a triangulation process, the sensor unit includes a position-sensitive receiving element capable of high speed, in order to measure the surface profile by deposition of the diffusely scattered light vertically to the object surface by means of telecentric projection.
16. The device according to claim 1 , wherein the object is movable relative to the sensor unit.
17. A process for inspecting a surface of an object to determine surface characteristics thereof, wherein light emitted from a sensor unit is transmitted to a scanning device and the emitted light is guided to and deflected by a deflecting element wherein the light deflected by the deflecting element is focused on the object by a concave mirror having a focal point and a symmetry axis, the light deflecting element being positioned at said focal point, said deflected light being guided under a constant angle relative to the symmetry axis of the concave mirror along a scanning line over the object, and light diffusely reflected from the object is generally guided back to the sensor unit along the same path as the emitted light, wherein the object surface is telecentrically projected into the sensor unit by the concave mirror, whereby the light deflecting element acts as an aperture diaphragm and wherein additionally the intensity of tracheid scattered light guided back to the sensor unit is measured by a receiver, the directly diffusely scatted light being blanked out for the receiver.
18. The process according to claim 17 , wherein the tracheid scattered light is measured by two receivers, each of said two receivers comprising a spatial filter for blanking out the directly diffusely scattered light point, the spatial filters being positioned orthogonally relative to one another to measure directional dependence of tracheid scattered light.
19. The process according to claim 17 , wherein for obtaining a 3D profile by a triangulation process, at least one light beam emitted by the sensor unit is guided on to the object and light directly diffusely scattered from the object under a constant angle ( ) relative to the incident beam is guided back to the sensor unit such that the incident beam and the guided back beam are coincident in a plane parallel to the surface of the object.
20. The process according to claim 17 , wherein various surface characteristics are measured in real time using parallel processors.
21. The process according to claim 17 , further comprising separating light portions of differing wave length impinging on the sensor unit from one another, and instantaneously recording, from the light portions, with a high repetition rate, various surface characteristics, said surface characteristics including elevation profile in a 3D channel, reflectivity in a red light channel, and tracheid effect in a scatter channel ( 15 ).
22. The process according to claim 21 , comprising splitting up light impinging on the sensor unit into first and second light portions, and guiding the first and second light portions to two light receivers, said first light portion having the image of the light cones of the scatter effect blanked out, the image of the directly diffusely reflected light point on the object is evaluated and from grey-scale image is obtained, and in the case of the second light portion, the directly diffusely reflected light point is blanked out by special spatial filters and only the image of the remaining light cones is evaluated by said receiver.
23. The process according to claim 22 , comprising the further steps of separating light portions of differing wave length impinging on the sensor unit from one another, whereby, with a first light portion in a triangulation process, 3D information is measured by means of a position sensitive receiving element and, with a second light portion, the intensity distribution of the object as well as the surface characteristics are measured with opto-electrical sensor elements.
24. The process according to claim 17 , wherein light impinging on the sensor unit makes density-dependent surface anomalies visible and, by means of a four-quadrant process, which is a function of the position (S x S y ) and the direction arctan (S x S y ) and, if necessary. in combination with the triangulation process in a 3D channel, which is a function of the elevation, is detected in a real time process, the spatial resolution of which is limited only by a focusing ability of the light.
25. The process according to claim 17 , further comprising moving the object relative to the sensor unit.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
January 10, 2000
September 10, 2002
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